The aim of the proposed research is to investigate the roles of cumulus cell steriods and cyclic adenosine monophosphate (cAMP) in the regulation of mammalian oocyte maturation. The following hypotheses will be tested: A relatively high ratio of estradiol (E2) to progesterone (P4) within the cumulus cell is required to maintain the coupling between the oocyte and its adherent cumulus cells; this coupling serves to maintsin the concentration of cAMP within the oocyte above a threshold level required to maintain meiotic arrest; an increase in synthesis by the cumulus cells of P4 relative to E2, results in disruption of this coupling and a subsequent reduction in the cAMP concentration within the oocyte below the threshold level required to prevent reinitiation of meiosis. A validated culture system will be used for this research, in which porcine cumulus cells synthesize E2 and P4, and the cumulus-enclosed oocytes exhibit reversible meiotic arrest. This system is composed of a complex serum-based medium that is supplemented with testosterone and follicle stimulating hormone. Oocytes will be cultured for 2 to 24 h, and meiotic status scored cytogenetically after preparation of chromatin spreads. The integrity of coupling between the oocyte and its adherent cumulus cells will be determined using a bioassay for intercellular communication involving radiolabeled markers; the presence of gap junctions between these heterologous cells will be assessed by electron microscopy. The concentrations of both E2, and P4 in the spent media, and that of cAMP within the oocyte and cumulus cell compartments will be determined by RIA. It is anticipated that this research will define the relationships which exist among cumulus cell steroids, maintenance of the integrity of cumulus-oocyte coupling and the role of cAMP in the regulation of maturation. The long-term objective is to elucidate the physiological mechanisms that regulate oocyte maturation. This process is fundamental to successful fertilizaion and consequent propagation of a species. Determination of these regulatory mechanisms is, therefor, essential if highly specific means of contraception are to be directed at the level of the oocyte, and if problems of human infertility related to oocyte development are to be clinically treated.